* Research [5/5] [100%]
** DONE Ruby docs

+ are located at: [[https://rubyapi.org/]]
+ lists classes and methods

** DONE The free online version of Programming Ruby: The Pragmatic Programmer's Guide [TFH08]

+ is located at: [[https://ruby-doc.com/docs/ProgrammingRuby/]]

** DONE A method that substitutes part of a string

+ [[https://rubyapi.org/3.1/o/string#method-i-gsub]]
+ [[https://rubyapi.org/3.1/o/string#method-i-initialize_copy]]

** DONE Information about Ruby's regular expressions

+ [[https://rubyapi.org/3.1/o/string]] under "Argument pattern" one can find the syntax and examples of regular expressions in Ruby.

** DONE Information about Ruby's ranges

+ official docs: [[https://rubyapi.org/3.1/o/range]]

* Do [6/6] [100%]
** DONE Print the string "Hello, world."
** DONE For the string "Hello, Ruby," find the index of the word "Ruby."
** DONE Print your name ten times.
** DONE Print the string "This is sentence number 1," where the number 1 changes from 1 to 10.
** DONE Run a Ruby program from a file.
** DONE Bonus problem

If you're feeling the need for a little more, write a program that
picks a random number. Let a player guess the number, telling the
player whether the guess is too low or too high.  (Hint: rand(10) will
generate a random number from 0 to 9, and gets will read a string from
the keyboard that you can translate to an integer.)
